Tone signal processing apparatus with intermittent clock supply

ABSTRACT

A music apparatus is constructed for processing a music tone signal in response to a clock signal at each sampling period. In the music apparatus, a clock generator generates the clock signal. A signal processor is operable in synchronization to the clock signal for time-divisionally processing a plurality of music tone signals through a plurality of channels within one sampling period. A clock controller is operative during a supply duration allocated within one sampling period for supplying the clock signal to the signal processor from the clock generator to thereby operate the signal processor, and is operative during other than the supply duration within one sampling period for stopping the supplying of the clock signal to the signal processor to thereby suspend the signal processor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a tone generator for use insuch apparatuses for generating tones as electronic musical instrumentsand amusement appliances. More particularly, the present inventionrelates to a tone signal processing apparatus for suitable in saving thepower consumption of these instruments and appliances.

2. Description of Related Art

With the recent enhancement in the performance of tone generators foruse in electronic musical instruments for example, the maximum number ofsounding channels and the level of operating clock frequencies growsteadily. This inevitably causes an increase in the number oftransistors and the number of transistor switching operations in a unittime in tone generator LSIs for example, thereby presenting a problem ofthe proportionally increased power consumption in these LSIs.Especially, with battery-driven electronic musical instruments, thelarge power consumption presents a serious problem which must be solvedto provide an operating life long enough for the general use of thesemusical instruments.

With CPUs for use in personal computer for example, a technology isknown by which the clock frequency is adjusted in accordance withoccasional processing loads. However, this technology has a drawback ofcomplicating the configuration of the clock circuits.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a tonesignal processing apparatus having a relatively simple configuration butcapable of reducing the power consumption in accordance with processingload.

According to the invention, an apparatus is constructed for processing amusic tone signal in response to a clock signal at each sampling period.The apparatus comprises a clock generator that generates the clocksignal, a signal processor operable in synchronization to the clocksignal for time-divisionally processing a plurality of music tonesignals through a plurality of channels within one sampling period, anda clock controller being operative during a supply duration allocatedwithin one sampling period for supplying the clock signal to the signalprocessor from the clock generator to thereby operate the signalprocessor, and being operative during other than the supply durationwithin one sampling period for stopping the supplying of the clocksignal to the signal processor to thereby suspend the signal processor.

Preferably, the inventive apparatus further comprises an allocatingdevice that allocates a predetermined supply duration within onesampling period, and a specifying device that specifies a detail ofprocessing of the music tone signals in accordance with thepredetermined supply duration so that the signal processor can completethe processing of the music tone signals within the predetermined supplyduration. In such a case, the allocating device allocates thepredetermined supply duration based on a predetermined number ofchannels through which music tones are generated concurrently by theprocessing of the music tone signals. Otherwise, the allocating deviceallocates the predetermined supply duration based on a predeterminednumber of steps by which a program is executed stepwise for processingthe music tone signals. Further, the specifying device specifies thedetail of the processing of the music tone signals in terms of a numberof channels through which the music tone signals are processed forconcurrent generation of music tones. Otherwise, the specifying devicespecifies the detail of the processing of the music tone signals interms of a kind of a program selectably executed by the signal processorin the processing of the music tone signals.

Preferably, the inventive apparatus further comprises a specifyingdevice that specifies a detail of processing of the music tone signals,and an allocating device that allocates a supply duration within onesampling period in accordance with the specified detail of theprocessing so that the signal processor can complete the specifieddetail of the processing of the music tone signals within the allocatedsupply duration. In such a case, the allocating device allocates thesupply duration in accordance with the specified detail of theprocessing in terms of a predetermined number of channels through whichmusic tones are generated concurrently by the processing of the musictone signals. Otherwise, the allocating device allocates the supplyduration in accordance with the specified detail of the processing interms of a predetermined number of steps by which a program is executedstepwise for processing the music tone signals. Further, the specifyingdevice specifies the detail of the processing of the music tone signalsin terms of a number of channels through which the music tone signalsare processed for concurrent generation of music tones. Otherwise, thespecifying device specifies the detail of the processing of the musictone signals in terms of a kind of a program selectably executed by thesignal processor in the processing of the music tone signals.

Preferably, the signal processor processes the music tone signal in sucha manner that waveform data of a designated timbre is read out togenerate the music tone signal at a designated pitch. Otherwise, thesignal processor processes the music tone signal in such a manner thatwaveform data is read out to generate the music tone signal and thegenerated music tone signal is subjected to filter processing.Alternatively, the signal processor processes the music tone signal insuch a manner as to control an amplitude of the music tone signal.Otherwise, the signal processor processes the music tone signal in sucha manner as to impart an effect to the music tone signal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the invention will be seen by reference tothe description, taken in connection with the accompanying drawings, inwhich:

FIG. 1 is a block diagram illustrating an electronic musical instrumentpracticed as a first embodiment of the invention;

FIG. 2 is a block diagram illustrating a tone signal line of a tonegenerator of the first embodiment;

FIG. 3 is a block diagram illustrating a clock signal line of the tonegenerator of the first embodiment;

FIGS. 4A, 4B, 4C, 4D, 4E, and 4F are timing charts showing operation ofa sounding channel clock controller and a DSP clock controller of thefirst embodiment;

FIG. 5 is a diagram illustration one example a power saving settingscreen of the first embodiment;

FIGS. 6A and 6B are flowcharts describing event processing in the powersaving setting screen of the first embodiment;

FIG. 7 is a flowchart describing note-on event processing of the firstembodiment;

FIGS. 8A and 8B are flowcharts describing event processing in an effectselect screen of the first embodiment;

FIGS. 9A and 9B are diagrams illustrating examples of the effect selectscreen of the first embodiment;

FIG. 10 is a block diagram illustrating a clock signal line of a tonegenerator of a second embodiment of the invention;

FIG. 11 is a block diagram illustrating a self power saving DSP of thesecond embodiment; and

FIGS. 12A, 12B, and 12C are flowcharts describing processing programs ofthe second embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

1. First Embodiment

1.1 Hardware Configuration

1.1.1 Overall Configuration

This invention will be described in further detail by way of examplewith reference to the accompanying drawings. First, a battery-drivenelectronic musical instrument practiced as a first embodiment of theinvention will be described. Referring to FIG. 1, there is shown anoverall configuration of this electronic musical instrument. In thefigure, references numeral 10 denotes a CPU, which control othercomponents of this electronic musical instrument through a bus (CPU busline) B. It should be noted that the bus B is a generic bus includingcontrol bus, data bus, and address bus. Reference numeral 11 denotes aROM for storing basic programs and various data for use by the CPU 10.Reference numeral 12 denotes a RAM for temporarily storing various datagenerated by control operations executed by the CPU 10. Referencenumeral 13 denotes a switch panel composed of various manual controlsfor selecting timbres of tones to be generated and for setting variousstates. Information specified through the switch panel 13 is supplied tothe CPU 10 through the bus B. Reference numeral 14 denotes a displayblock which is constituted by a CRT or an LCD panel to display, underthe control of the CPU 10, the information inputted from the switchpanel 13 and currently set information.

Reference numeral 15 denotes play controls, which includes a musickeyboard, a pitch-bend wheel, and a pedal for example. Each key of thekeyboard is arranged with a key sensor (not shown) for detecting a playoperation by a player made on the keyboard. Each key sensor supplies, tothe CPU 10 through the bus B, resultant key information such as a keycode KC indicative of the pitch of a pressed key, key-on KON indicativeof the generation of a tone when a key is pressed, key-off KOFFindicative of the damping of a tone when a key is released, and velocityVEL indicative of a speed at which a key is pressed. Reference numeral16 denotes a storage medium such as an FDD (Floppy Disk Drive) or an HDD(Hard Disk Drive) for recording various data and programs. Referencenumeral 19 denotes a clock circuit for supplying a clock signal to othercomponents of the electronic musical instrument. Reference numeral 20denotes a MIDI interface for transferring MIDI signals with externalMIDI devices. Reference numeral 22 denotes a battery-based power supplyblock.

Reference numeral 200 denotes a tone generator which provides 64sounding channels in a time division manner, generates a tone signal ineach channel, and performs a predetermined effect algorithm to impart aneffect to a generated tone signal. To achieve this purpose, the tonegenerator 200 incorporates a DSP (Digital Signal Processor) for effectimpartment. Reference numeral 250 denotes a waveform memory storingplural pieces of basic waveform data for each timbre. Reference numeral260 denotes an external circuit, which is a unit for supplying a tonesignal, other than the tone generator 200, or a unit such as anexternally connected effector. Reference numeral 270 is a delay memorywhich is used by the built-in DSP. A tone signal generated by the tonegenerator 200 is converted by a DC converter 17 into an analog signal,which is then externally sounded through a sound system 18 composed ofan amplifier, a loudspeaker, and so on.

1.1.2 Tone Signal Line in Tone Generator

The following describes a tone signal line in the tone generator 200with reference to FIG. 2. In the figure, reference numeral 201 denotes acontrol register & controller for controlling other components of thetone generator under instruction by the CPU 10 through the bus B. A readcircuit 202 reads from the waveform memory 250 the waveform data of aspecified timbre by executing address manipulation such that the readwaveform data provide a pitch specified by a key code KC. A DCF (DigitalControl Filter) 206 executes various filtering operations on thewaveform data read by the read circuit 202.

A volume controller 203 controls the amplitude or envelope of thewaveform data supplied through the DCF 206 such that the waveform dataprovide a loudness specified by velocity VEL, thereby providing a tonegenerator output before effect impartment. The read circuit 202, the DCF206 and the volume controller 203 can operate in the time-divided 64channels for generating a different tone signal in each channel. The CPU10 allocates a note to one of the 64 channels when a sounding commandsuch as key pressing occurs, and writes tone control data forcontrolling tone generation according to this sounding command to achannel area allocated by the control register & controller 201. On thebasis of the written tone control data, the read circuit 202 and thevolume controller 203 generate a tone accordingly. It should be notedthat, from the volume controller 203, the generated tone from eachchannel is outputted to a mixer 210 under multiplexing state of64-channel time division at every sampling frequency.

The mixer 210 executes predetermined processing on the tone signalsinputted from the volume controller 203 and an tone signal inputted fromthe external circuit 260, and outputs a resultant signal to DSP 205 andthe external circuit 260. Also, of the outputs to the DSP 205, the mixer210 returns given output signals of some channels to the read circuit202 through the line. The read circuit 202 can write the returned signalto the RAM area of the waveform memory as new data. As described, theDSP 205 imparts sound effects to the tone signals. A tone signal for 4channels, a part of the result of this effect processing, is supplied tothe DA converter 17 shown in FIG. 1, thereby providing a final output ofthis electronic musical instrument. It should be noted that the outputof the electronic musical instrument is given in the form of the outputof the DSP 205 because the final stage of this electronic musicalinstrument is an equalizer, one of the effect blocks constructed in theDSP 205.

The following briefly describes a method of computation practiced in theDSP 205. The DSP 205 has a program memory (not shown) for storingmicroprograms. The present embodiment assumes that the maximum number ofsteps constituting one microprogram be 1024, the maximum number of inputchannels of the waveform data to be processed be 16, and the maximumnumber of output channels of the processed waveform data be also 16. Thechannels (input and output channels) as used in the DSP 205 aredifferent in concept from the sounding channels as used in the readcircuits 202 and the volume controller 203. Namely, a sounding channelis generated and allocated every time a note-on event is supplied fromthe play controls 15 or the MIDI interface 20. The input channel in theDSP 205 is used for receiving the waveform data which is inputted fromthe mixer 210 to the DSP 205, for example, a result of mixing thesewaveform data for each part (each timbre). The output channel outputs tothe mixer 210 the waveform data on which processing such as effectimpartment has been executed in the DSP 205. A technology for channelswitching on a time-division basis is detailed in Japanese PublishedUnexamined Patent Application No. Hei 11-85155 and corresponding U.S.patent application Ser. No. 09/115,616, for example.

At the starting of every sampling period, the mixing results of themixer 210 (the waveform data resulted from the mixing processingexecuted by the mixer 210 in the last sampling period) are sequentiallyread by the DSP 205 and stored in a register of the DSP 205. The DSP 205sequentially executes signal processing on the stored waveform data ofeach input channel as instructed by the microprogram starting with itsfirst step. If, this signal processing requires to delay the waveformdata for a relatively long time, the DSP 250 writes the waveform data tobe delayed into the delay memory 270, and reads the waveform datapreviously written in the delay memory 270 during the sampling periodcorresponding to the delay time, thereby realizing the delay processing.Thus, the DSP 205 executes the signal processing based on themicroprogram consisting of the maximum of 1024 steps on the waveformdata for the maximum of 16 input channels, thereby outputting thewaveform data for the maximum of 16 output channels to the mixer 210. Asdescribed, the DSP 205 supplies the computational results for thepredetermined 4 channels to the DA converter 17 shown in FIG. 1 as afinal tone signal.

The following briefly describes sound effects treated in the presentembodiment. The effects may be classified into three blocks ofreverberation, chorus, and variation. In each block, one of the effectsas shown in FIG. 9A for example can be selected. Any one signal can beselected from the above-mentioned 16 channels, and supplied to eacheffect (it is also practicable to allocate two or more channels to oneeffect). One or more output signals resulted from each effect processingcan be set so that they are outputted from any of the above-mentioned 16output channels and the 4 channels of the DA converter 17 (it is alsopracticable to supply the output of one effect block to two or morechannels). Namely, a signal level to be supplied to each effect can beset for each tone signal of each part. It is also practicable tocontinuously connect effects with each other. A specific example thereofis disclosed in the above-mentioned patent application.

1.1.3 Clock Signal Line in Tone Generator

The following describes a clock signal line in the tone generator 200with reference to FIG. 3. In the figure, a clock signal φ is supplied toone input terminal of each of AND gates 221 through 224. Mask signals Sathrough Sd are supplied to the other input terminals of the AND gates221 through 224, respectively. Consequently, the clock signal φ issupplied to the read circuit 202, the DCF 206, the volume controller203, and the DSP 205 while the mask signals Sa through Sd are placed atlogical “1”, respectively (namely, during a supply period). In theremaining periods, the clock signal φ is not supplied, so that thesecomponents of the tone generator are held in the stopped state.

Reference numeral 231 denotes a sounding channel clock controller, whichreceives channel control data from the CPU 10, and outputs theabove-mentioned mask signals Sa through Sc on the basis of the receiveddata. The channel control data denote numeric data 0 through 64indicative of how many channels are permitted to work among the maximumof 64 channels. In FIGS. 4A through 4C, the waveforms of the masksignals Sa through Sc are illustrated when the channel control data are64, 48, and 32, respectively.

In FIG. 4A, all sounding channels (64) are valid, so that the masksignals Sa through Sc are always at logical “1”. In FIG. 4B, 48 soundingchannels are valid, so that the duty ratios of the mask signals Sathrough Sc are, respectively, approximately 48/64. It should be notedthat these duty ratios are slightly greater than 48/64. This is becausethe read circuit 202, the DCF 206, and the volume controller 203 executepipeline processing, in which these duty ratios correspond to a durationof a time between the starting of the first stage of the pipelineprocessing by a sounding channel to be processed first and the ending ofthe final stage of the pipeline processing of another sounding channelto be processed last. For example, a duration of time between thestarting and ending of the processing of one sounding channel is longerthan 1/64 of the sampling frequency.

It should also be noted that the mask signals Sb and Sc are eachslightly delayed in phase behind the mask signal Sa. These delays areprovided to make the mask signals correspond to the above-mentioned timedelay in the pipeline processing. Referring to FIG. 4C, 32 channels aremade valid, so that, as with the example shown in FIG. 4B, the dutyratios of the mask signals Sa through Sc are, respectively, slightlygreater than 32/64.

Returning back to FIG. 3, reference numeral 232 denotes a DSP clockcontroller, which receives DSP control data from the CPU 10, and outputsthe above-mentioned mask signal Sd on the basis of the received signal.The DSP control data denote numeric data 0 through 1024 indicative ofthe number of steps (up to 1024) permitted for the microprogram. FIGS.4D through 4F show the waveforms of the mask signal Sd when the DSPcontrol data are 1024, 768, and 512, respectively. Referring to FIG. 4D,all sounding steps (1024) are made valid, so that the mask signal isalways at logic “1”. The duty ratios of the mask signal Sd shown in FIG.4E and 4F are slightly greater than 768/1024 and 512/1024, respectively,due to the pipeline processing in the DSP 205. These values correspondto a duration of time between the starting of the first stage of thepipeline processing by a step of the microprogram to be executed firstand the ending of the final stage of the pipeline processing of anotherstep to be processing last.

According to the invention, as described above, the inventive musicapparatus is constructed for processing a music tone signal in responseto a clock signal at each sampling period. In the music, a clockgenerator in the form of the clock circuit 19 generates the clocksignal. A signal processor is provided in the form of the tone generator200 including the read circuit 202, DCF 206, volume controller 203 andDSP 205, and is operable in synchronization to the clock signal φ fortime-divisionally processing a plurality of music tone signals through aplurality of channels within one sampling period. A clock controller isprovided in the form of the channel clock controller 231 and the DSPclock controller 232. The clock controller is operative during a supplyduration determined by the mask signals Sa-Sd and allocated within onesampling period for supplying the clock signal to the signal processorfrom the clock generator to thereby operate the signal processor, and isoperative during other than the supply duration within one samplingperiod for stopping the supplying of the clock signal to the signalprocessor to thereby suspend the signal processor.

Referring to FIG. 3 again, the volume controller 203 incorporates an EGmemory 203a for storing a current volume level of each sounding channel.To this memory, an unmasked clock signal φ is supplied. Because the EGmemory 203a is referenced by the CPU 10 from time to time as required(for releasing sounding channels, for example), the EG memory 203a iskept in an active state by this clock signal such that the EG memory203a is always accessible by the CPU 10. The unmasked clock signal φ isalso supplied to the mixer 210. This is because the mixer 210 executes atime division operation different from the sounding channels andmicroprogram steps, thereby making it impossible to simply stop thisoperation of the mixer 210 on the basis of channel control data and DSPcontrol data.

1.2 Operation of First Embodiment

1.2.1 Note-on Event Processing

The following describes operation of the present embodiment. First, whenthe electronic musical instrument (EMI) is powered on, the EMI is placedin the play mode. When the user presses a key on the play controls 15 orwhen a note-on signal is supplied through the MIDI interface 20, anote-on event is generated, upon which a program shown in FIG. 7 isexecuted by the CPU 10.

Referring to FIG. 7, when the process goes to step SP32, the partnumber, note-number, and velocity of the newly generated note-on eventare substituted into variables PT, NN, and LEV, respectively. Next, instep SP34, among the channels determined by variable CHM, a channelcorresponding to this note-on event is allocated. The number of theallocated sounding channel is substituted into variable AS.

Variable CHM denotes the permitted number of sounding channels. Asdefault, this variable is initialized to the maximum number of channels.CHMax (64) of the present electronic musical instrument. Namely, in stepSP 34, if the number of channels currently sounded is smaller than thepermitted number of channels CHM, a new channel is allocated to a newnote-on event. On the other hand, if the number of channels currentlysounded is equal to the permitted number of sounding channels CHM, theCPU 10 references the EG memory 203a and acquires the volume level ofeach sounding channel. The CPU 10 detects a channel having the lowestvolume level and frees or releases this channel. The CPU 10 allocates anew note-on event to the freed channel.

In step SP36, sounding parameters in accordance with the part number PT,note number NN, and velocity VEL are set to a tone generator register(not shown) of the channel number AS in the control register &controller 201. In step SP38, sounding is instructed to start the tonegenerator register of the channel number AS. Subsequently, in the tonegenerator 200, a tone waveform is synthesized by the read circuit 202,the DCF 206 and the volume controller 203 for that sounding channel. Thesynthesized tone waveform is imparted with an effect by the DSP 205 asrequired, and the resultant tone signal is sent to the sounding system18 to be sounded.

1.2.2 Displaying of Power Saving Setting Screen

When the user executes a predetermined operation in the play mode, apower saving setting screen shown in FIG. 5 appears on the display block14. In FIG. 5, reference numeral 31 denotes a CPU setting section inwhich three options “SLOW”, “MEDIUM”, and “FAST” are selectivelyarranged for the operating clocks of the CPU 10. Reference numeral 32denotes a block for setting the permitted number of sounding channels inwhich three options 32, 48 and 64 are arranged. Reference numeral 33denotes a block for setting the permitted number of steps in which threeoptions 512, 758 and 1024 are arranged as the number of steps permittedfor the microprogram of the DSP 205.

(1) Event processing for inputting the permitted number of soundingchannels:

Operating the switch panel 13, the user can select an option in eachsetting block. The following describes, with reference to FIG. 6A, theprocessing to be executed when the permitted number of channels ischanged on the setting block 32 for setting the permitted number ofsounding channels.

Referring to FIG. 6A, in step SP2, the newly inputted permitted numberof sounding channels is substituted into variable CHM. Next, in stepSP4, this permitted number of sounding channels CHM is compared with thechannel control data. If the permitted number of channels CHM is foundlower than the channel control data, the decision is NO. Then, in stepS8, the permitted number of channels CHM is set to the tone generatorregister as new channel control data. Consequently, in the soundingchannel clock controller 231, the on/off timings of the mask signals Sathrough Sc are set on the basis of the new channel control data.

On the other hand, if the decision is YES in step SP4, then the CPU 10waits until the sounding of all shortfall sounding channels goes off instep SP6. This will be further described by use of the case where thechannel control data are 64 and the permitted number of channels CHM hasbeen changed to 48 for example. Because the channel control data are 64,it is likely that sounding channels 49 through 64 are sounding at thispoint of time. If the channel control data are immediately set to 48,the clock signal φ is masked for the channels 49 through 64, so that thevolume of that sounding channel immediately becomes zero, therebygenerating a shock noise. In order to prevent the shock noise from beinggenerated, the CPU 11 monitors the volume levels of the soundingchannels (49 through 64) which may be in sounding state and should beturned off, and the CPU 11 keeps the processing in the standby stateuntil all of the volume levels of the overloaded channels 49-64 go belowa predetermined value (as low as zero). Only thereafter, the processinggoes to step SP8, so that the channel control data can be reducedwithout generating a shock noise.

(2) Event processing for inputting the permitted number of steps:

The following describes the processing to be executed when the userchanges the permitted number of steps with reference to FIG. 6B. In thefigure, the inputted permitted number of steps is substituted intovariable STM in step SP10. Next, in step SP12, it is determined whetherthe number of steps STM has been decreased below the DSP control dataand some of the effect processes have become unexecutable. If thedecision is NO, then, in step SP20, this permitted number of steps STMis set to the tone generator register in the control register &controller 201 as new DSP control data. Subsequently, the on/off timingof the mask signal Sd is set on the basis of the new DSP control data.

On the other hand, if the decision is YES in step SP12, then the name ofan effect to be disabled and an inquiry message whether to forciblyeffect through the reduction of the permitted number of steps aredisplayed on the display block 14 in step SP14. For example, assume thatthe DSP control data be 1024 and “HALL1” (350 steps) as reverberation.“CHORUS1” (350 steps) as chorus, and “ROTARY SPEAKER” (300 steps) asvariation be stored in this order at address 0 through 1000 in theprogram memory of the microprogram.

If the permitted number of steps STM newly set is 768, the execution ofvariation “ROTARY SPEAKER” of the above-mentioned effects is disabled.In this case, therefore, a message “Insufficient number of steps; do youwant to delete variation ROTARY SPEAKER?” is displayed on the displayblock 14, and the CPU 10 waits until the user inputs an answer. When theuser inputs the answer, then, in step SP16, it is determined whether theanswer of the user is for effecting the deletion of the effect. If thedecision is NO, the permitted number of steps STM is not reflected asthe DSP control data, upon which this routine comes to an end.

On the other hand, if the decision is YES in step SP16, then the outputof the effect (ROTARY SPEAKER) to be disabled is damped (namely,gradually reduced to zero) in step SP18 and the microprogramcorresponding to the canceled steps is deleted from the program memoryof the DSP 205. Subsequently, in step SP20, this permitted number ofsteps STM is set to the tone generator register as new DSP control data.

1.2.3 Displaying of Effect Select Screen

(1) Updating of menu display

When the user executes a predetermined operation in the play mode, aneffect select menu display update routine (FIG. 8A) for specifyingand/or changing effects is called. Referring to FIG. 8A, in step SP42,the number of steps set in the current DSP control data and the numberof steps actually used in the microprogram are detected. In step SP44,subtraction is executed between these numbers of steps to detect thenumber of free steps in the number of set steps in the DSP control data.

In step SP46, on the basis of the number of free steps and a state ofeffect selection, a menu (changeable effect options) of each effect isdetermined and the determined menu is listed on the display block 14.FIG. 9A shows one example of this display. In the figure, “HALL2” isselected as reverberation, “CHORUS3” as chorus, and “GATE REVERB” asvariation (the selections are highlighted in reverse). The effects notselected are also displayed. This indicates that these unselectedeffects can be selected for the currently selected effect. Namely, evenif the select state is changed, the total number of steps of themicroprogram will not exceed the DSP control data.

(2) Effect select event processing

When the user selects an effect in the effect select screen (FIG. 9A),select switching processing is executed accordingly. For one example ofthis processing, processing executed when a reverberation change isspecified will be described with reference to FIG. 8B. In the flowchart,in step SP52, the number of a newly selected reverberation is stored invariable REVN. In step SP54, the reverberation block of the DSP 205 ismuted.

In step SP56, a microprogram corresponding to the reverberation numberREVN is loaded in the microprogram memory of the DSP 205. In step SP58,the reverberation block of the DSP 205 is recovered from the mutedstate. In step SP60, the effect select menu display update routine (FIG.8A) is called again to display an effect select screen with a changedreverberation onto the display block 14. With the chorus and variationeffects, the similar processing is executed to update the contents ofdisplay on the display block 14. In each block, if “NO EFFECT” isselected, the microprogram of the effects of the selected block is freedin step SP56. To be specific, this block is filled with NOP (NoOperation) codes.

Thus, the user can select or deselect any effect in each effect blockwithin a range permitted by the DSP control data. It should be notedthat the effect select screen shown in FIG. 9A assumes that the DSPcontrol data be 1024 (the maximum number of steps). FIG. 9B shows aneffect select screen to be displayed when the DSP control data are lessthan 1024; for example, 512. In the figure, reverberation “HALL2” andvariation “ECHO” have been selected already. In the reverberation blockand the variation block of the effect select screen, selectable effects(the total number of steps not exceeding 512) are listed in addition tothe already selected effects. In this case, however, the number ofselectable effects is smaller than those listed in the screen shown inFIG. 9A. This is because only the effects of comparatively small numberof steps can be loaded in the microprogram memory.

In the chorus block, only “NO EFFECT” is displayed. This indicates thatthere is no room for adding any chorus effect, because the reverberationand variation effects have been set already. However, if eitherreverberation or variation is set to “NO EFFECT” for example, thecorresponding microprogram is unloaded and one or more chorus effectswhich can be loaded in the resultant free steps are displayed in theeffect select screen.

As described with reference to the first embodiment, in the inventiveapparatus, an allocating device is provided in the form of the switchpanel 13. As exemplified by the blocks 31 and 32 shown in FIG. 5, theallocating device allocates a predetermined supply duration within onesampling period. Further, as exemplified by the channel number limitingStep SP34 of FIG. 7 and effect designation limiting step shown in FIGS.9A and 9B, a specifying device specifies a detail of processing of themusic tone signals in accordance with the predetermined supply durationso that the signal processor can complete the processing of the musictone signals within the predetermined supply duration. In such a case,the allocating device allocates the predetermined supply duration basedon a predetermined number of channels through which music tones aregenerated concurrently by the processing of the music tone signals.Otherwise, the allocating device allocates the predetermined supplyduration based on a predetermined number of steps by which a program isexecuted stepwise for processing the music tone signals. Further, thespecifying device specifies the detail of the processing of the musictone signals in terms of a number of channels through which the musictone signals are processed for concurrent generation of music tones.Otherwise, the specifying device specifies the detail of the processingof the music tone signals in terms of a kind of a program selectablyexecuted by the signal processor in the processing of the music tonesignals.

2. Second Embodiment

The following describes an electronic musical instrument practiced as asecond embodiment of the invention. The hardware and softwareconfigurations of the second embodiment are generally the same as thoseof the first embodiment. Therefore, the following describes only thedifferences from the first embodiment.

2.1 Hardware Configuration of Second Embodiment

A clock signal line of a tone generator 200 of the second embodimentwill be described with reference to FIG. 10.

In the figure, reference numeral 235 denotes a sounding channel clockcontroller, which is provided in place of the sounding channel clockcontroller 231 of the first embodiment. In the sounding channel clockcontroller 235, channel control data are 64 bits long.

These bits correspond to 0 to 64 sounding channels, respectively, logic“1” denoting that sounding of that channel is enabled and logic “0”denoting that sounding of that channel is disabled. Therefore, dependingon a bit pattern, periods of supplying the clock signal φ in which themask signals Sa through Sc go logic “1” may be scattered in one samplingperiod. Reference numeral 215 denotes a self power saving DSP, which isprovided in place of the DSP 205 of the first embodiment. To the selfpower saving DSP 215, the clock signal φ is supplied without beingmasked.

The following describes a configuration of the self or auto power savingDSP 215 with reference to FIG. 11. In the figure, reference numeral 52denotes a counter which is reset in every sampling period to count theclock signal φ. A count result is supplied to a microprogram memory 54as a read address. Reference numeral 56 denotes an instructioninterpreting block for interpreting an instruction code read from themicroprogram memory 54. The block 56 makes a computing block 62 executevarious computational operations on the basis of the interpretation. Inthe second embodiment, special instructions called “clock-on” and“clock-off” are included in an instruction code set.

When the instruction interpreting block 56 detects a clock-oninstruction, it sets an RS flip-flop 58. When the instructioninterpreting block 56 detects a clock-off instruction, it rests the RSflip-flop 58. Reference numeral 60 denotes an AND gate which executes anAND operation between an output signal Q of the RS flip-flop 58 and theclock signal φ, and supplies a result to the computing block 62 as aclock signal. Therefore, once a clock-off instruction is detected by theinstruction interpreting block 56, no clock signal is supplied to thecomputing block 62 until a clock-on instruction is detected next,thereby stopping the operation of the computing block 62, resulting inthe reduction of power consumption during that period.

2.2 Operations of Second Embodiment

2.2.1 Note-on Event Processing

In the second embodiment, when a note-on event occurs, a routine shownin FIG. 12A is executed instead of the routine shown in FIG. 7.Referring to FIG. 12A, in step SP72, the part number, note number, andvelocity of the newly generated note-on event are substituted intovariables PT, NN, and VEL, respectively. In step SP74, one of the 64channels is allocated to the note-on event.

The following describes the rules of the allocation. If all of the 64channels are currently sounding (namely all of the 64 channels have avolume level above a predetermined value), the sounding channel havingthe lowest volume level is freed. The note-on event is allocated to thisfreed sounding channel. On the other hand, if there are two or moresounding channels having volume levels lower than the predeterminedvalue, the sounding channel having the lowest channel number isallocated. As described, because the read circuit 202, the DCF 206, andvolume controller 203 execute pipeline processing, a time from startingthe processing of one sounding channel to ending the same is equal to orlonger than 1/64 of sampling period. Therefore, the processing of eachsounding channel is overlapped with that of another sounding channel onthe time axis by allocating the sounding channel having a channel numberas low as possible, thereby lowering the duty ratios of the mask signalsSa through Sc, respectively.

In step SP76, as with the first embodiment, the sounding parameterscorresponding to part number PT, note number NN, and velocity VEL areset to a tone generator register (not shown) for channel number AS in acontrol register & controller 201. In doing so, an AS bit of the channelcontrol data is set to logic “1”. In step SP78, sounding is instructedto start for the tone generator register of the channel number AS.Subsequently, in the tone generator 200, a tone waveform is synthesizedfor the sounding channel. The synthesized tone waveform is imparted withan effect as required and the resultant tone signal is sent to asounding system 18 to be sounded.

2.2.2 Timer Interrupt Processing

In the second embodiment, a timer interrupt occurs for the CPU 10 atevery predetermined time (one second for example), thereby starting theexecution of a timer interrupt processing routine shown in FIG. 12C. Inthe figure, in step SP95, the contents of the EG memory 203a aresearched for a sounding channel of which volume level is less than apredetermined value. The bit of the channel control data whichcorresponds to this channel is set to logic “0”.

2.2.3 Displaying of Power Saving Setting Screen

When the user executes a predetermined operation in the play mode, apower saving setting screen is also displayed in the second embodiment.In this embodiment, however, only the CPU setting section 31 isdisplayed on the display block 14. Hence, there is no processingcorresponding to the processing shown in FIGS. 6A and 6B of the firstembodiment.

2.2.4 Displaying of Effect Screen

(1) Updating of menu display

In the second embodiment also, when the user executes a predeterminedoperation, the effect select menu display update routine (FIG. 8A) forspecifying and/or changing effects is called. In the second embodiment,however, “the maximum number of steps (1024)” is used for “the number ofsetting steps in current DSP control data” used in the first embodiment.Consequently, the menus of the effects to be displayed on the displayblock 14 are always as shown in FIG. 9A, and the limited menu display asshown FIG. 9B is not displayed.

(2) Effect select event processing

In the second embodiment also, when the user selects an effect in theeffect select screen (FIG. 9A), corresponding select switchingprocessing is executed. The following describes this processing by useof an example in which the user specifies a change of reverberationeffects, with reference to FIG. 12B. In the figure, the processing ofsteps SP82 through SP86, the processing of SP88, and the processing ofSP90 are generally the same as those of steps SP52 through SP56, theprocessing of step SP58, and the processing of SP60.

In the second embodiment, however, processing of step SP87 is providedunlike the first embodiment. In step SP87, a microprogram loaded orunloaded in step SP86 is checked for detecting an inactive range (forexample, a range filled with NOP codes) which is equal to or greaterthan the predetermined number of steps. If this inactive range isdetected, a clock-off instruction is added to a location several stepsafter the first NOP code. These several steps are provided, because itis necessary to wait for the complete end of the pipeline processing ofan instruction immediately before the first NOP code. Further, for thesame reason, a clock-on signal is added to a location several stepsbefore the end of the inactive range in step SP87. Therefore, when thismicroprogram is executed, the operation of the computing block 62 stopsin the interval between the clock-off code and the clock-on code,thereby reducing the power consumption. This holds true with the changeand/or freeing of chorus and variation effects.

As described with reference to the second embodiment, in the inventiveapparatus, a specifying device specifies a detail of processing of themusic tone signals, as exemplified by effect selecting screen of FIG. 9Aand channel allocation step SP74 of FIG. 12A. Further, an allocatingdevice allocates a supply duration within one sampling period inaccordance with the specified detail of the processing so that thesignal processor can complete the specified detail of the processing ofthe music tone signals within the allocated supply duration. Such anoperation is exemplified by step SP76 of FIG. 12A and SP87 of FIG. 12B.

Thus, according to the second embodiment, the supply of the clock signalφ can be automatically stopped according to the occasional states ofsounding channels and the effects without limiting the number ofsounding channels and the selectable effects at all, thereby achievingpower saving. This makes it unnecessary for the user to be aware of thepower consumption of the electronic musical instrument and therefore theuser can concentrate only on music-related jobs.

3. Modifications

The preferred invention is not limited to the above-mentionedembodiments. For example, the following various modifications may bemade.

(1) The effect select screen of the first embodiment lists only theselectable effects according to occasional situations as shown in FIGS.9A and 9B. It will be apparent to those skilled in the art that alleffects are listed and the unselectable effects are displayed in anadequate manner (for example, in an inconspicuous manner) to preventthem from being selected.

(2) In the effect select screen of the first embodiment, the number ofeffect blocks to be displayed may be changed according to the permittednumber of steps. For example, if the permitted number of steps is 1024,all blocks are displayed; if it is 768, two blocks are displayed; and,if it is 512, only one block is displayed. The block to be displayedwhen the permitted number of steps is less than 1024 may be a systemdefault block or one or two user-selected blocks.

(3) In the second embodiment, the values of the channel control databits are switched by the CPU 10. It will be apparent to those skilled inthe art that this processing may be executed inside the tone generator200 by arranging a channel monitor circuit therein. To be more specific,the channel monitor circuit sequentially reads the volume levels of thesounding channels from the EG memory 203a to determine whether eachvolume level is equal to or greater than a predetermined level (as lowas zero). For the sounding channels with their volume levels found equalto or greater than the predetermined level, the corresponding channelcontrol bit may be set to logic “1”. For the other sounding channels,the corresponding channel control bit may be set to logic “0”.

However, it is desirable to exclude from the above-mentioned decision,exceptional sounding channels of which volume levels are temporarily lowdue to the operation of a volume control such as a volume pedal.Therefore, it is preferable to store, for all channels, 64-wordexclusion data in the channel monitor circuit, the data being indicativeof whether to exclude the channel from the decision. To be morespecific, any sounding channel of which exclusion data are logic “1” isexcluded from the decision and therefore the corresponding channelcontrol data bit does not go logic “0”. On the other hand, for anysounding channel of which exclusion data are logic “0”, thecorresponding channel control data bit is set according to the volumelevel of that sounding channel.

In addition, when such control operations may be executed in reading thewaveform data of the attack section and loop section from the waveformmemory, a channel is excluded from the decision until the attack sectionhas been read (for example, if the exclusion data=2). Otherwise, after asounding channel is noted on, the sounding channel is excluded from thedecision until it is noted off (for example, if the exclusion data=3).

(4) In the second embodiment, the CPU 10 detects the range filled withNOP codes in the microprogram (namely the range not effectively used forthe effect processing), and accordingly adds the clock-on and clock-offinstructions to the microprogram. Alternatively, the clock-on andclock-off instructions may be automatically executed in the tonegenerator 200. For example, referring to FIG. 11, the instructioninterpreting block 56 may be configured so that, upon detection that thepredetermined number of NOP codes are continuously lined, theinstruction interpreting block 56 resets the RS flip-flop 58;subsequently, upon detection, by executing instruction look ahead, of aninstruction other than NOP at a location several steps later, theinstruction interpreting block 56 sets the RS flip-flop 58.

(5) Many recent electronic musical instrument DSPs are each configuredas a multi-DSP which executes two or more effect processing operationsin parallel (as disclosed in Japanese Published Unexamined PatentApplication No. Hei 10-198560 and corresponding U.S. Pat. No. 6,085,309,for example). In this case, it is preferable that control data be setfor controlling the supply of an operating clock for each of two or moremicroprograms executed in parallel. To be more specific, in an operationat every DSP sampling, the operating clock is supplied during a periodin which a microprogram for which the control data are set to “supply”and the operating clock is not supplied during a period in which thecontrol data are set to “not supply”.

(6) In each of the above-mentioned embodiments, if “NO EFFECT” isselected in any effect block, the microprogram for the effects in thateffect block is filled with NOP codes. Alternatively, instead of fillingwith NOP codes, a microcode for that portion may be configured so thatit does not affect other microcodes in execution, for example.Alternatively still, data generated by the microcode for that portionmay be prevented from being finally outputted as a tone signal. Thesetwo alternatives can be easily implemented by disabling a writeoperation to the internal registers of the DSP 205 and the delay memory270 for that portion of the microcode.

4. Species

The present invention is embodied in the following manners.

(1) A tone generating apparatus operating on the basis of an operatingclock, comprises a tone generating block for generating tone signals forplural sounding channels in a time division manner, a control datainputting block for inputting control data for controlling the number ofabove-mentioned plural sounding channels, a clock control block forcontrolling, on the basis of the above-mentioned control data, thesupply of the operating clock to the tone generating block, and asounding control block for allocating, in accordance with a soundingstart instruction, sounding of a tone signal corresponding to thissounding start instruction to all or some of the above-mentionedsounding channels to be determined on the basis of the above-mentionedcontrol data and starting the generation of the above-mentioned tonesignal in the allocated sounding channels.

According to the above-mentioned novel constitution, the power to thetone generator for generating tone signals for plural sounding channelsin a time division manner can be saved only by adding a simpleconfiguration to a related-art tone generator.

(2) A signal processing apparatus for executing operations of pluralsteps for every sampling period on the basis of an operating clock,comprises a signal processing block for executing signal processing, acontrol data input block for inputting the number of steps of aprocessing operation to be executed by the signal processing block, aclock control block for controlling, on the basis of the above-mentionedcontrol data, the supply of the operating block to the signal processingblock, and a processing program selecting block for selecting a programto be executed by the signal processing block in a range of the numberof steps determined in accordance with the control data and for settingthe selected program to the signal processing block.

According to the above-mentioned novel constitution, the power to thesignal processor for executing operations of plural steps in everysampling period can be saved only by adding a simple configuration to arelated-art signal processor.

(3) A tone generating apparatus operating on the basis of an operatingclock, comprises a tone generating block for generating tone signals forplural sounding channels in a time division manner, a sounding controlblock for allocating, in accordance with a sounding start instruction,the sounding of a tone signal corresponding to this sounding startinstruction to any of the above-mentioned plural sounding channels andstarting the generation of this tone signal in the allocated soundingchannel, a volume detecting block for detecting a volume level of eachof the above-mentioned plural sounding channels, a control datagenerating block for generating, on the basis of the detected volumelevel of each sounding channel, control data for controlling the supplyof the operating clock for each sounding channel, and a clock controlblock for controlling, on the basis of the above-mentioned control data,the supply of the operating clock to the above-mentioned tone generatingblock.

According to the above-mentioned novel constitution, the supply of theoperating clock to the tone generator on the basis of the volume levelof each sounding channel, thereby maximizing the power saving of thetone generator.

(4) A signal processing apparatus for executing operations of pluralsteps in every sampling period on the basis of an operating clock,comprises a signal processing block for executing signal processing, aprocessing program selecting block for selecting a program to beexecuted by the above-mentioned signal processing block and setting theselected program to the signal processing block, a control datagenerating block for generating, on the basis of the set program,control data indicative of a program range not valid or effective inthis program, and a clock control block for preventing, on the basis ofthe above-mentioned control data, a part of the clocks from beingsupplied to the signal processing block.

According to the above-mentioned novel constitution, the operating clockis supplied only for a period in which a valid program is beingexecuted, thereby maximizing the power saving of the signal processor.The valid program herein denotes a program in which a result of signalprocessing (for example, effect processing) executed by that program hasbeen converted into a perceivable tone.

As described and according to the invention, the supply of a clocksignal to a processing circuit can be controlled in synchronization witha sampling period, thereby reducing the power consumption of theprocessing circuit in accordance with processing load by a simpleconfiguration.

While the preferred embodiment of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the appendedclaims.

1. An apparatus for processing a music tone signal in response to aclock signal at each sampling period, the apparatus comprising: a clockgenerator that generates the clock signal; a signal processor operablein synchronization to the clock signal for time-divisionally processinga plurality of music tone signals through a plurality of tone generatingchannels within one sampling period; and a clock controller beingoperative during a supply duration allocated within one sampling periodfor supplying the clock signal to the signal processor from the clockgenerator to thereby operate the signal processor, and being operativeduring other than the supply duration within one sampling period forstopping the supplying of the clock signal to the signal processor tothereby suspend the signal processor, wherein the supply duration isallocated to correspond with one or more of tone generating channelswhich are allowed to generate music tones.
 2. The apparatus according toclaim 1, further comprising an allocating device that allocates apredetermined the supply duration within one sampling period, and aspecifying setting device that specifies a detail of processing of themusic tone signals in accordance with the predetermined supply durationso that the signal processor can complete the processing of the musictone signals within the predetermined supply duration operates based onmusic data which commands generating of music tones, and that sets oneor more of tone generating processes based on the music data to one ormore of the plurality of the tone generating channels whichtime-divisionally process the music tone signals within the allocatedsupply duration.
 3. The apparatus according to claim 2, wherein theallocating device allocates the predetermined supply duration based on apredetermined number of tone generating channels through which musictones are generated concurrently by the processing of the music tonesignals.
 4. The apparatus according to claim 2, wherein the allocatingdevice allocates the predetermined supply duration based on apredetermined number of steps by which a program is executed stepwisefor processing the music tone signals.
 5. The apparatus according toclaim 2, wherein the specifying setting device specifies the detail ofthe processing of the music tone signals in terms of a number of selectsone tone generating channel from the tone generating channels throughwhich the music tone signals are processed for concurrent generation ofmusic tones through which the signal processor can generate music tonesby the clock signal supplied in the supply duration among the pluralityof the tone generating channels, and sets the tone generating process tothe selected tone generating channel.
 6. The apparatus according toclaim 2, wherein the specifying device specifies the detail of theprocessing of the music tone signals in terms of a kind of a programselectably executed by the signal processor in the processing of themusic tone signals.
 7. The apparatus according to claim 1, furthercomprising a specifying setting device that specifies a detail ofprocessing of the music tone signals, operates based on music data whichcommands generating of music tones, and that sets one or more of tonegenerating processes based on the music data to one or more of theplurality of the tone generating channels, and an allocating device thatallocates a supply the supply duration within one sampling period inaccordance with the specified detail of the processing so that thesignal processor can complete the specified detail of the processing ofthe music tone signals within the allocated supply duration tonegenerating process set by the setting device.
 8. The apparatus accordingto claim 7, wherein the allocating device allocates the supply durationin accordance with the specified detail of the processing in terms of apredetermined number of channels through which music tones are generatedconcurrently by the processing of the music tone signals the settingdevice selects one tone generating channel from the plurality of thetone generating channels, and sets the tone generating process to theselected tone generating channel.
 9. The apparatus according to claim 7,wherein the allocating device allocates the supply duration inaccordance with the specified detail of the processing in terms of apredetermined number of steps by which a program is executed stepwisefor processing the music tone signals.
 10. The apparatus according toclaim 7, wherein the specifying device specifies the detail of theprocessing of the music tone signals in terms of a number of channelsthrough which the music tone signals are processed for concurrentgeneration of music tones.
 11. The apparatus according to claim 7,wherein the specifying device specifies the detail of the processing ofthe music tone signals in terms of a kind of a program selectablyexecuted by the signal processor in the processing of the music tonesignals.
 12. The apparatus according to claim 1, wherein the signalprocessor processes the music tone signal in such a manner that waveformdata of a designated timbre is read out to generate the music tonesignal at a designated pitch.
 13. The apparatus according to claim 1,wherein the signal processor processes the music tone signal in such amanner that waveform data is read out to generate the music tone signaland the generated music tone signal is subjected to filter processing.14. The apparatus according to claim 1, wherein the signal processorprocesses the music tone signal in such a manner as to control anamplitude of the music tone signal.
 15. The apparatus according to claim1, wherein the signal processor processes the music tone signal in sucha manner as to impart an effect to the music tone signal.
 16. A methodof processing a music tone signal in response to a clock signal at eachsampling period, the method comprising the steps of: continuouslygenerating the clock signal; operating a signal processor insynchronization to the clock signal for time-divisionally processing aplurality of music tone signals through a plurality of tone generatingchannels within one sampling period; supplying the generated clocksignal to the signal processor so as a to operate the signal processorduring a supply duration allocated within one sampling period; andstopping the supplying of the generated clock signal to the signalprocessor so as to suspend the signal processor during other than thesupply duration within one sampling period, wherein the supply durationis allocated to correspond with one or more of tone generating channelswhich are allowed to generate music tones.
 17. A medium for use in amusic apparatus having a signal processor for processing a music tonesignal in response to a clock signal at each sampling period, the mediumcontaining program instructions executable by the music apparatus toperform a method comprising the steps of: continuously generating theclock signal; operating the signal processor in synchronization to theclock signal for time-divisionally processing a plurality of music tonesignals through a plurality of tone generating channels within onesampling period; supplying the generated clock signal to the signalprocessor so as a to operate the signal processor during a supplyduration allocated within one sampling period; and stopping thesupplying of the generated clock signal to the signal processor so as tosuspend the signal processor during other than the supply durationwithin one sampling period, wherein the supply duration is allocated tocorrespond with one or more of tone generating channels which areallowed to generate music tones.
 18. The apparatus according to claim 1further comprising a setting device that operates based on music datawhich commands generating of music tones, and that sets one or more oftone generating processes based on the music data to one or more of theplurality of the tone generating channels, wherein in case that a tonegenerating process is set to a tone generating channel, the clockcontroller starts supplying of the clock signal for a period necessaryfor the tone generating channel to generate music tones so that the tonegenerating channel of the clock signal for the period when the volumelevel of the music tones generated by the tone generating channelbecomes less than a predetermined value.
 19. The method according toclaim 16 further comprising the step of setting one or more of tonegenerating processes to one or more of the tone generating channelsbased on music data which commands generating of music tones, wherein incase that a tone generating process is set to a tone generating channel,the supplying step starts supplying of the clock signal for a periodnecessary for the tone generating channel to generate music tones sothat the tone generating channel starts the generating of the musictone, and the stopping step stops supplying of the clock signal for theperiod when the volume level of the music tones generated by the tonegenerating channel becomes less than a predetermined value.
 20. Themedium according to claim 17, wherein the method further comprises thestep of setting one or more of tone generating processes to one or moreof the tone generating channels based on music data which commandsgenerating of music tones, wherein in case that a tone generatingprocess is set to a tone generating channel, the supplying step startssupplying of the clock signal for a period necessary for the tonegenerating channel to generate music tones so that the tone generatingchannel starts the generating of the music tone, and the stopping stepstops supplying of the clock signal for the period when the volume levelof the music tones generated by the tone generating channel becomes lessthan a predetermined value.